What would u do, (if you do) if u had 2 stop cussing for the rest of ur life?

Well, if you don't use profanity and they do, and they insist on using it, I'd look toward the future and encourage them to go for it. As you've obviously caught on to and noticed here, as people mature the begin to see profanity as immature and uneducated. You've got to have seen it, when someone is speaking publically, or says something profane when they think they're talking privately but aren't, what's the focus? I've seen it happen, a person approaches the podium at a council meeting to speak, begin their statements and suddenly, BAM, a bad speaking habit pops out, sheer force of habit because they use it all the time. Suddenly, nothing they have to say matters, their time is wasted, all people have heard, all they will remember, is That Word. All credibility is gone. So, encourage all those losers to use profanity, let it become a sloppy speaking habit, because one day, maybe a few years down the road, you may be competing with them for a job, or speaking somewhere opposing them for something, and guess what, the person who screws up loses.
I'll admit something here, I've used this against people, especially younger people. It's not a secret that profanity has become all too commonplace in their language, so if it comes up to a debate on an issue, I'll begin to pressure them, start making them think and respond faster than they're normally accustomed to, and when they're pressured they focus on what they want to say, not what they're actually saying, their brain outpaces their mouth, and many times, BAM, there it is, they blow it, their credibility is blown, everyone forgets anything else they said. It doesn't have to be pointed out, everyone has heard it, the speaker knows he screwed up, his confidence is shot, his concentration broken, he falters, his message is lost and I win. Dirty, maybe so, but in the game of life you use all the legitimate tools at your disposal to accomplish your goals, and your mouth will be used against you. It's called Hung by the Tongue.
So, as you grow up, keep this in mind, in the real world you are continually judged, and how you speak is an important part of that. These school mates WILL one day be your competition and the stakes can be, often are, high. You make the decisions in your life, be just like them, or strive to be on the more winning edge. Strive to purge profanity completely from your vocabulary and you will be able to present yourself with confidence, more articulate because you can entirely focus on your message knowing your presentation comes naturally. Don't be afraid to study English.
They're right, your not their boss ...Yet.
Think about it.